Temperature and humidity variations in burial stone relics can easily cause water vapor condensation, which is an important factor leading to their deterioration. However, the water vapor condensation mechanism and the evaluation of risk ratings have always been difficult problems in the protection of cultural relics. In this study, the water vapor condensation mechanism in Yang Can's tomb was comprehensively investigated through on-site monitoring, indoor experiments and software simulations, on the basis of which a physical model of water vapor condensation in this tomb was established and a water vapor condensation risk rating assessment method was proposed. The proposed method considers the difference between the dew point and wall temperatures within the tomb (dew–wall temperature difference) and the duration of water vapor condensation, and corresponding preventive and control measures were formulated for different risk ratings. The study revealed that when the wall temperature of the chamber is lower than the dew point temperature, water vapor starts to condense. The larger the dew–wall temperature difference is, the greater the risk of condensation. In addition, specific water vapor condensation prevention and control measures were proposed for Yang Can's tomb, and the prevention and control effects were simulated. The simulation results showed that favorable prevention and control effects could be achieved, and the proposed measures could be applied in practice. This study holds notable significance for investigating the water vapor condensation mechanism and evaluating the risk ratings of burial stone relics and provides a theoretical basis and reference for water vapor condensation prevention and control in burial stone relics.